Unit Cell Titanium Casting

ABSTRACT

A system ( 5 ) and method ( 800 ) for unit cell casting of titanium or titanium-alloys is disclosed herein. The system ( 5 ) comprises an external chamber ( 45 ), a crucible ( 10 ) positioned within the external chamber ( 45 ), an induction coil ( 15 ) positioned around the crucible, an internal chamber ( 40 ) positioned within the external chamber ( 45 ), and a mold ( 30 ) positioned within the internal chamber ( 40 ). The external chamber ( 45 ) is evacuated and a pressurized gas is injected into the evacuated external chamber ( 45 ) to create a pressurized external chamber ( 45 ). An ingot ( 20 ) is melted within the crucible utilizing induction heating generated by the induction coil ( 15 ). The internal chamber ( 40 ) is evacuated to create an evacuated internal chamber ( 40 ). The titanium alloy material of the ingot ( 20 ) is completely transferred into the mold ( 30 ) from the crucible ( 10 ) using a pressure differential created between the external chamber ( 45 ) and the internal chamber ( 40 ).

CROSS REFERENCES TO RELATED APPLICATIONS

The present application claims priority to U.S. Provisional PatentApplication No. 62/440,033 filed on Dec. 29, 2016, U.S. ProvisionalPatent Application No. 62/440,040 filed on Dec. 29, 2016, and U.S.Provisional Patent Application No. 62/440,038 filed on Dec. 29, 2016,each of which is hereby incorporated by reference in its entirety.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to precision titanium casting. Morespecifically, the present invention relates to an apparatus and methodfor precision titanium casting utilizing induction heating.

Description of the Related Art

Various methods of titanium casting are well-known. One such method isinvestment casting which involves a lost wax procedure.

Vacuum electric arc smelting is another method in which a titanium ingotis melted by substantial heat generated by mutual discharging in a highcurrent state by respectively using a titanium ingot crucible and awater-cooled copper crucible as a positive electrode and a negativeelectrode, thereby forming a molten liquid metal in the crucible andcompleting the casting of the titanium.

Another method is vacuum induction smelting in which an induction coilis wrapped outside a split-type water-cooled copper crucible. Theelectromagnetic force generated by the induction coil passes through anonmetal isolation portion between splits of the copper crucible andthen acts on a titanium ingot placed inside the crucible. Then themolten metal forms a molten metal liquid inside the crucible and thecasting of the titanium is completed.

Vacuum induction smelting and vacuum electric arc smelting require theuse of a water-cooled copper crucible which results in the loss ofsubstantial heat. The actual power consumed is very little (only 20% to30% of the power actually acts on the titanium). Furthermore, thepreparation of the molding shell is very complex and time consuming,which adds to the costs. In the traditional casting technology, theoperation time of a single furnace is usually 60 to 80 minutes, and theloading and discharge process requires the coordination of many people.In the traditional casting technology, the process from the preparationof the wax pattern to the clearing of the molding shell can take tendays.

Titanium is an extremely reactive metal. During melting via traditionalcasting processes, a water cooling environment is required. The moltentitanium liquid will come into direct contact with water if the cruciblecracks, resulting in a fierce reaction, or even explosion, which poses agreat threat to production safety.

To solve the above problems, a new kind of titanium alloy inductionmelting vacuum suction casting device is urgently needed, to solve theproblems with existing titanium alloy casting, such as low efficiency,high cost, complicated technology, heavy workload, difficulty withpreparing high-quality molding shells, long cycle and potential hazard.

BRIEF SUMMARY OF THE INVENTION

Utilizing the two chamber casting system, one of the primary tenets isthe use of a crucible in order to contain the target material duringmelt and prior to evacuation into the pattern mold. In order toaccelerate the melting of the target material and reduce cycle times, itis necessary to preheat the crucible to higher temperatures (>500 C).This causes a faster heating and subsequent melting of the targetmaterial thus reducing the time necessary to evacuate the material fromthe crucible into the pattern mold. The accelerated process also reducesthe potential for reaction of the target material and may allow for morecomplete fill of complex geometries.

One aspect of the present invention is a method for unit cell casting oftitanium or titanium-alloys. The method includes positioning a moldwithin an internal chamber. The method also includes evacuating anexternal chamber to create an evacuated external chamber wherein aceramic crucible containing a titanium alloy ingot is positionedtherein. The method also includes evacuating the internal chamber tocreate an evacuated internal chamber having a pressure no greater than3×10⁻² atmosphere. The method also includes injecting a pressurized gasinto the evacuated external chamber to create a pressurized externalchamber with a pressure in excess of 1 atm. The method also includespre-heating the crucible to a temperature greater than 500° C. Themethod also includes melting the titanium alloy ingot within the ceramiccrucible utilizing induction heating generated by an induction coil,wherein a position of the induction coil begins at a upper third of thetitanium alloy ingot and during the melting of the titanium alloy ingotthe position of the induction coil is lowered relative to the titaniumalloy ingot to terminate at a bottom of the titanium alloy ingot. Themethod also includes transferring the completely melted titanium alloymaterial into the mold from the crucible using a pressure differentialcreated between the external chamber and the internal chamber. A highpressure differential in maintained between the external chamber and theinternal chamber during the transfer of the melted titanium alloymaterial. The PLC controls power to the induction coil to superheat thetitanium alloy ingot in the ceramic crucible, and the PLC also controlsthe positioning of the induction coil. The placement of the inductioncoil first acts on the upper portion of the ingot melting the materialfrom the top down, causing molten material to cascade around thestill-solid ingot and forming a seal before the electromagnetic forcesof the induction coil affect the remaining material. The pressure of theinternal chamber and the pressure of the external chamber are monitoredand communicated to the PLC during the casting process, and wherein thePLC controls the casting process based on the pressure of the internalchamber and the pressure of the external chamber.

Another aspect of the present invention is a system method for unit cellcasting of titanium or titanium-alloys. The system comprises an externalchamber, a ceramic crucible positioned within the external chamber, aninduction coil positioned around an upper third of the ingot within theceramic crucible, an internal chamber positioned within the externalchamber, a mold positioned within the internal chamber, a first vacuumgauge positioned within the internal chamber, a second vacuum gaugepositioned within the external chamber, a PLC in communication with thefirst vacuum gauge, the second vacuum gauge, and the induction coil. Thecrucible is preheated to a temperature greater than 500° C. The pressureof the internal chamber and the pressure of the external chamber aremonitored and communicated to the PLC during the casting process, andwherein the PLC controls the casting process based on the pressure ofthe internal chamber and the pressure of the external chamber. Placementof the induction coil first acts on the upper portion of the ingotmelting the material from the top down, causing molten material tocascade around the still-solid ingot and forming a seal before theelectromagnetic forces of the induction coil affect the remainingmaterial. The external chamber is evacuated to create an evacuatedexternal chamber wherein the ceramic crucible contains a titanium alloyingot positioned therein. A pressurized gas is injected into theevacuated external chamber to create a pressurized external chamber. Thetitanium alloy ingot is melted within the ceramic crucible utilizinginduction heating generated by the induction coil positioned around theceramic crucible, wherein a power for the induction coil is commences ata first power level of 15 kiloWatts and increases to a second powerlevel greater than 50 kiloWatts. The internal chamber is evacuated tocreate an evacuated internal chamber. The titanium alloy material iscompletely transferred into the mold from the crucible using a maximumpressure differential created between the external chamber and theinternal chamber. The titanium alloy ingot is preferably centered withinthe ceramic crucible using a centering feature. The centering feature ispreferably a plurality of stand-offs in a wall of the ceramic crucible.

Yet another aspect of the present invention is a method for unit cellcasting of titanium or titanium-alloys. The method includes evacuatingan external chamber to create an evacuated external chamber wherein aceramic crucible containing a titanium alloy ingot is positionedtherein. The method also includes evacuating the internal chamber tocreate an evacuated internal chamber having a pressure no greater than3×10⁻² atmosphere. The method also includes melting the titanium alloyingot within the ceramic crucible utilizing induction heating generatedby an induction coil wherein a position of the induction coil begins ata upper third of the titanium alloy ingot and during the melting of thetitanium alloy ingot the position of the induction coil is loweredrelative to the titanium alloy ingot to terminate at a bottom of thetitanium alloy ingot. The method also includes injecting a pressurizedgas into the evacuated external chamber to create a pressurized externalchamber with a pressure in excess of 1 atmosphere, wherein the pressuredifferential is at a maximum. The method also includes utilizing a highpressure differential between the external chamber and the internalchamber to flow the completely melted titanium alloy material into themold from the crucible.

The pressurized gas is preferably argon. The mold is preferably coveredin a kaolin wool insulating material. The mold is preferably for athin-walled golf club head. The mold is alternatively for an articlehaving a wall thickness less than 0.250 inch. The induction melting timepreferably ranges from 30 seconds to 90 seconds. The ceramic crucible ispreferably composed of two yttria-based primary crucible layers, whereina first primary crucible layer has a thickness ranging from 0.010 inchto 0.060 inch, and a second primary crucible layer has a thicknessranging from 0.001 inch to 0.020 inch. The ceramic crucible furthercomprises a silica based backup layer. The induction coil is preferablypositioned around a bottom section of the ceramic crucible. Theinduction coil is alternatively positioned around an upper section ofthe ceramic crucible.

Having briefly described the present invention, the above and furtherobjects, features and advantages thereof will be recognized by thoseskilled in the pertinent art from the following detailed description ofthe invention when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is an illustration of a unit-cell casting system.

FIG. 2 is an isolated view of an interior chamber, crucible, inductioncoils and mold of the unit-cell casting system, showing placement of theinduction coils at a lower section of the crucible.

FIG. 2A is an isolated view of an interior chamber, crucible, inductioncoils and mold of the unit-cell casting system, showing placement of theinduction coils at an upper section of the crucible.

FIG. 2B is an isolated view of an interior chamber, crucible, inductioncoils and mold of the unit-cell casting system, showing an insulationmaterial wrapped around the mold.

FIG. 3A is an illustration of a technician pre-heating a mold in anoven.

FIG. 3B is an illustration of a technician attaching the pre-heated moldto a lid of the internal container.

FIG. 3C is an illustration of a technician attaching the lid to theinternal container.

FIG. 3D is an isolated view of the internal container.

FIG. 3E is an isolated view of the lid of the internal container.

FIG. 3F is an isolated view of the internal chamber of the internalcontainer showing infrared heaters.

FIG. 4 is an illustration of a unit-cell casting system during anexternal chamber evacuation step.

FIG. 4A is an illustration of a unit-cell casting system during anexternal chamber pressurization step.

FIG. 4B is an illustration of a unit-cell casting system during an ingotmelting step.

FIG. 5 is an illustration of a PLC unit and computer for a unit cellcasting system.

FIG. 6 is a block diagram of a unit cell casting method.

FIG. 7 is an isolated view of a crucible for a unit cell casting system.

FIG. 8 is a flow chart of a method for unit cell titanium casting.

FIG. 9 is a flow chart of a method for unit cell titanium casting.

FIG. 10 is a flow chart of a method for unit cell titanium casting.

FIG. 11 is an illustration of a PLC unit, an operator's computer for aunit cell casting system, an internal chamber with monitoringconnections.

FIG. 12 is an illustration of a PLC unit, an operator's computer for aunit cell casting system, an internal chamber with monitoringconnections.

DETAILED DESCRIPTION OF THE INVENTION

Utilizing the two chamber casting system, one of the primary tenets isthe use of a crucible in order to contain the target material duringmelt and prior to evacuation into the pattern mold. In order toaccelerate the melting of the target material and reduce cycle times, itis necessary to preheat the crucible to higher temperatures (>500 C).This causes a faster heating and subsequent melting of the targetmaterial thus reducing the time necessary to evacuate the material fromthe crucible into the pattern mold. The accelerated process also reducesthe potential for reaction of the target material and may allow for morecomplete fill of complex geometries.

Utilizing the two chamber casting system, one of the primary tenets isthe use of a crucible in order to contain the target material duringmelt and prior to evacuation into the pattern mold. In order to ensureuniform heating of the target material it is necessary to have the ingotcentered within the crucible. This is achieved by the incorporation of acentering feature (ideally a “seat” in the crucible base, but possiblestandoffs in the crucible walls) in the crucible itself. This allows forconsistent ingot placement resulting in uniform and predictable meltingof the target material which in turn results in more consistent finalparts.

Utilizing the two chamber casting system, one of the primary tenets isthe use of a crucible in order to contain the target material duringmelt and prior to evacuation into the pattern mold. In order to reduceoperating costs while still allowing the electromagnetic forces from theinduction coil to act upon the target material, the crucible should beformed of a molded crucible formed of >90% Yttria. This will allow forthe crucible to be reused and also minimize any reaction between thecrucible and the target material during melt.

Utilizing the two chamber casting system, one of the primary tenets isthe use of a crucible in order to contain the target material duringmelt and prior to evacuation into the pattern mold. In order to reduceoperating costs while still allowing the electromagnetic forces from theinduction coil to act upon the target material, the crucible should beformed of a molded crucible formed of >90% Zirconia. This will allow forthe crucible to be reused and reduce overall cost due to crucible usageand materials.

Utilizing the two chamber casting system, one of the primary tenets isthe use of a crucible in order to contain the target material duringmelt and prior to evacuation into the pattern mold. In order to reduceoperating costs while still allowing the electromagnetic forces from theinduction coil to act upon the target material, the crucible ispreferably formed of a molded crucible formed of Yttria and infused withBarium. This will provide the benefits of a molded Yttria crucible(reusable, low reactivity) with the benefit of the target material beingless apt to stick to the surface thus providing better evacuation andhigher chance of reuse.

As shown in FIG. 1, a unit cell titanium casting system 5 comprises anexternal container 44, an internal container 39, a vacuum mechanism 60,a crucible 10, an induction coil 15, a coil electrical generationmechanism 25, and a mold 30. The external container 44 defines anexternal chamber 45. The internal container 39 defines an internalchamber 40. The vacuum mechanism 60 includes a vacuum line 71, a vacuumconnector 70 and pressure gauges 75 a and 75 b. The vacuum mechanism 60is utilized to evacuate and pressurize the external chamber 45 and theinternal chamber 40 in order to create a pressure differential betweenthe internal chamber 40 and the external chamber 45.

The crucible 10 is preferably composed of a ceramic material. In a mostpreferred embodiment, the crucible 10 is composed of a first layer 11 a,a second layer 11 b and a silica based third layer 11 c, as shown inFIG. 7. A metal ingot 20 is placed within the interior of the crucible10. The metal ingot 20 is preferably a titanium alloy material. Thevolume of the crucible 10 preferably corresponds to the amount of metalnecessary for forming the article. The interior of the crucible 10preferably has a diameter ranging from 15 centimeters (“cm”) to 90 cm,more preferably from 35 cm to 60 cm. A height of the crucible 10preferably ranges 30 cm to 200 cm, and more preferably from 60 cm to 100cm.

A connection nozzle 27 is connected between a bottom opening (not shown)of the crucible 10 and an opening to the mold 30. The connection nozzle27 allows the melted metal material from the ingot 20 to flow into themold 30 for casting of the article. Specifically, the size of connectionnozzle 27 is determined based on the size and shape of the cavity of themold 30, and is preferably from 5 cm to 100 cm, and more preferably from15 cm to 50 cm.

The induction coil 15 is wrapped around the crucible 10. The inductioncoil 15 is energized to generate an electromagnetic force to melt themetal ingot 20 (e.g., titanium alloy ingot) within the crucible 10. Thecoil electrical generation mechanism 25 provides the electricity to theinduction coil 15. As shown in FIG. 2, the induction coil 15 is wrappedaround a bottom section 10 b of the crucible 10. This melts the bottomof the ingot 20 first. As shown in FIG. 2A, the induction coil 15 iswrapped around an upper section 10 a of the crucible 10. This melts thetop of the ingot 20 first.

In order to optimize the ability of the target material to seal aroundthe port of a ceramic crucible 10, the induction coil 15 is preferablycentered on the upper third of the ingot 20. This positioning allows theinduction coil 15 to first act on the upper portion of the ingot 20(melting the material from the top down), causing molten material tocascade around the still-solid ingot 20 and forming a seal before theelectromagnetic forces of the induction coil 15 affect the remainingmaterial.

Alternatively, in order to fully utilize the electromagnetic forces ofthe induction coil 15, to include the electromagnetic stirring of themelt, the induction coil 15 is positioned towards the bottom 10 b of theceramic crucible 10. This positioning allows for a uniform melt asmolten material cascades onto itself and also increased homogeneity ofthe pour as the electromagnetic forces can better act on the moltenmaterial prior to it being evacuated from the crucible 10.

Melting of the ingot 20 of titanium alloy is carried out in a vacuumcondition for induction melting. The induction coil 15 is connected tothe coil electrical generation mechanism 25.

The ceramic crucible 10 is utilized for vacuum induction melting of thetitanium alloy. The ceramic material does not interfere with thefielding effect of the electromagnetic force, and the electro-magneticinduction energy generated by the induction coil 15 is fully focused onmelting the ingot of titanium alloy.

In an embodiment shown in FIG. 2B, an insulating material 31 is wrappedaround the mold 30. During casting pattern molds are preheated prior touse in order to improve the flow of material into the mold itself and tobetter allow the mold 30 to fill completely. Due to the nature oftitanium materials, and the melting process itself, the more that heatloss is minimized, the greater time the material has to flow and fillthe mold 30 prior to solidification. To this end, pattern mold heat isretained through the use of an insulating material 31 (e.g.: Kaolinwool) thereby extending the useful period of the mold 30 prior to thepour and allowing for better fill, including filling of more difficultmolds (e.g., thin walled castings).

As shown in FIGS. 3A, 3B, 3C, 3D and 3E, the mold 30 is preheated in anoven 80. During unit cell casting, pattern molds 30 are preheated priorto use in order to improve the flow of material into the mold 30 itselfand to better allow the mold 30 to fill completely. Due to the nature oftitanium materials, and the melting process itself, there is a likelycorrelation between the temperature of the mold 30 and the ability tofill complex and/or thin walled pattern molds 30. Temperatures testinginclude 1050° C., 1060° C., 1100° C., 1150° C., 1200° C., 1250° C. and1260° C. The pre-heated mold is removed from the 80 and attached to alid 35 of the internal container 39.

In an alternative embodiment shown in FIG. 3F, infrared heaters 50 a and50 b are used to maintain the heat of the mold 30 within the internalchamber 40. Due to the nature of titanium materials, and the meltingprocess itself, the more that heat loss is minimized, the greater timethe material can flow and fill the mold 30 prior to solidification. Tothis end, pattern mold heat is retained through the use of infraredheaters 50 a and 50 b placed within the internal walls of the internalchamber 40 of the internal container 39 in order to minimize patternmold cool down and improve the ability to cast complex and/orthin-walled parts.

FIGS. 4, 4A and 4B illustrate the casting process using a pressuredifferential between the external chamber 45 and the internal chamber 40to assist in the flow of melted titanium alloy materials into a mold 30.

FIG. 5 illustrates a programmable logic computer (“PLC”) and operatorcomputer 91 utilized with the unit cell casting system 5.

FIG. 6 is a block diagram of a unit cell casting method 600. At step601, an ingot 20 is prepared for casting. The single ingot 20 isutilized to manufacture a single article such as a golf club head 29. Asopposed to manufacturing multiple articles in a single process, whichresults in the loss of material, the present invention manufactures onlya single article in each process. At step 602, the mold 30 is preheatedin an oven. At step 603, the external chamber 45 is evacuated. At step604, the external chamber 45 is pressurized with an argon gas. At step605, the internal chamber 40 is evacuated. At step 606, the inductioncoil 15 is energized and at step 607 the ingot 20 is melted within thecrucible 10. At the step 608, the melted material flows into mold 30. Atstep 609, the de-molding process occurs. At step 610, the article (golfclub head) 29 is finished. A frequency generated in the induction coilranges from 1 kilo-Hertz to 50 kilo-Hertz, and a power ranges from 15kilo-Watts to 50 kilo-Watts. An atmospheric pressure of the evacuatedinternal chamber ranges from 3×10⁻² atmosphere to 9.87×10⁻⁷ atmosphere.An atmospheric pressure of the evacuated internal chamber ranges from9.87×10⁻⁷ atmosphere to 9.87×10⁻¹³ atmosphere.

As shown in FIG. 7, the first layer 11 a and the second layer 11 b arepreferably composed of yttrium oxide and other materials. Yttrium oxideis highly inert to titanium in a high-temperature environment resultingin no chemical reaction between the two materials. Yttrium oxide alsoisolates the ceramic material from the titanium during the meltingprocess to prevent reaction between them to ensure the smooth melting ofthe titanium-alloy. The third layer 11 c of the crucible 10 ispreferably composed of silicon dioxide and other materials. The silicondioxide resists the metallic expansion and thermal stress during themelting process to ensure strength of the crucible.

A preferred thickness of the first layer 11 a is from 0.5 mm to 1.5 mmand the preferred thickness range of the crucible 10 is from 5 mm to 15mm.

A method 800 for unit cell casting of titanium or titanium-alloys isshown in FIG. 8. At block 801, a pressure of an internal chamber ismonitored utilizing a first vacuum gauge. At block 802, a pressure of anexternal chamber is monitored utilizing a second vacuum gauge. At block803, the pressure of the internal chamber and the pressure of theexternal chamber are transmitted to a programmable logic controller(PLC). At block 804, a mold is positioned within the internal chamber.At block 805, an external chamber is evacuated to create an evacuatedexternal chamber having a pressure no greater than 3×10⁻² atmosphere,wherein a ceramic crucible containing a titanium alloy ingot ispositioned therein. At block 806, the internal chamber is evacuated tocreate an evacuated internal chamber having a pressure no greater than3×10⁻² atmosphere, wherein the external chamber and the internal chamberhave an equal pressurization. At block 807, the titanium alloy ingot ismelted within the ceramic crucible utilizing induction heating generatedby an induction coil positioned around the ceramic crucible. At block808, the completely melted titanium alloy material is transferred intothe mold from the crucible using a pressure equalization between theexternal chamber and the internal chamber. A pressure equalization ismaintained between the external chamber and the internal chamber duringthe melting of the titanium alloy ingot. The pressure of the internalchamber and the pressure of the external chamber are monitored andcommunicated to the PLC during the casting process, and wherein the PLCcontrols the casting process based on the pressure of the internalchamber and the pressure of the external chamber.

A method 900 for unit cell casting of titanium or titanium-alloys isshown in FIG. 9. At block 901, a pressure of an internal chamber ismonitored utilizing a first vacuum gauge. At block 902, a pressure of anexternal chamber is monitored utilizing a second vacuum gauge. At block903, the pressure of the internal chamber and the pressure of theexternal chamber are transmitted to a programmable logic controller(PLC). At block 904, a mold is positioned within the internal chamber.At block 905, an external chamber is evacuated to create an evacuatedexternal chamber having a pressure no greater than 3×10⁻² atmosphere,wherein a ceramic crucible containing a titanium alloy ingot ispositioned therein. At block 906, the internal chamber is evacuated tocreate an evacuated internal chamber having a pressure no greater than3×10⁻² atmosphere, wherein the external chamber and the internal chamberhave an equal pressurization. At block 907, the titanium alloy ingot ismelted within the ceramic crucible utilizing induction heating generatedby an induction coil positioned around the ceramic crucible. At block908, a pressurized gas is injected into the evacuated external chamberto create a pressurized external chamber with a pressure in excess of 1atm, wherein the pressure differential between the external chamber andthe internal chamber is maximized. At block 909, the completely meltedtitanium alloy material is transferred into the mold from the crucibleusing a pressure equalization between the external chamber and theinternal chamber. A high pressure differential in maintained between theexternal chamber and the internal chamber during the transfer of themelted titanium alloy material. The pressure of the internal chamber andthe pressure of the external chamber are monitored and communicated tothe PLC during the casting process, and wherein the PLC controls thecasting process based on the pressure of the internal chamber and thepressure of the external chamber.

A method 1000 for unit cell casting of titanium or titanium-alloys isshown in FIG. 10. At block 1001, a mold is positioned within an internalchamber of a casting chamber. At block 1002, an external chamber isevacuated to create an evacuated external chamber wherein a ceramiccrucible containing a titanium alloy ingot is positioned therein. Atblock 1003, the internal chamber is evacuated to create an evacuatedinternal chamber having a pressure no greater than 3×10⁻² atmosphere. Atblock 1004, the titanium alloy ingot is melted within the ceramiccrucible utilizing induction heating generated by an induction coilpositioned around the ceramic crucible, wherein the external chamber andthe internal chamber are at an equal pressurization. At block 1005, apressurized gas is injected into the evacuated external chamber tocreate a pressurized external chamber with a pressure in excess of 1atmosphere. At block 1006, a high pressure differential is utilizedbetween the external chamber and the internal chamber to flow thecompletely melted titanium alloy material into the mold from thecrucible.

FIG. 11 illustrates a PLC 90, an operator's computer 91 and an apparatus5 for a system for unit cell titanium casting.

FIG. 12 illustrates a PLC 90, an operator's computer 91 and an internalchamber with an optical pyrometer for a system for unit cell titaniumcasting. The optical pyrometer monitors the temperature of the internalchamber.

Those skilled in the pertinent art will recognize that materials otherthan titanium and titanium alloy may be cast in the unit cell castingsystem without departing from the scope and spirit of the presentinvention.

From the foregoing it is believed that those skilled in the pertinentart will recognize the meritorious advancement of this invention andwill readily understand that while the present invention has beendescribed in association with a preferred embodiment thereof, and otherembodiments illustrated in the accompanying drawings, numerous changes,modifications and substitutions of equivalents may be made thereinwithout departing from the spirit and scope of this invention which isintended to be unlimited by the foregoing except as may appear in thefollowing appended claims. Therefore, the embodiments of the inventionin which an exclusive property or privilege is claimed are defined inthe following appended claims.

We claim as our invention the following:
 1. A method for unit cellcasting of titanium or titanium-alloys, the method comprising:positioning a mold within an internal chamber; evacuating an externalchamber to create an evacuated external chamber wherein a ceramiccrucible containing a titanium alloy ingot is positioned therein;evacuating the internal chamber to create an evacuated internal chamberhaving a pressure no greater than 3×10⁻² atmosphere; injecting apressurized gas into the evacuated external chamber to create apressurized external chamber with a pressure in excess of 1 atm;pre-heating the crucible to a temperature greater than 500° C.; meltingthe titanium alloy ingot within the ceramic crucible utilizing inductionheating generated by an induction coil; transferring the completelymelted titanium alloy material into the mold from the crucible using apressure differential created between the external chamber and theinternal chamber; wherein a high pressure differential in maintainedbetween the external chamber and the internal chamber during thetransfer of the melted titanium alloy material; wherein the PLC controlspower to the induction coil to position the induction coil relative tothe titanium alloy ingot; wherein the pressure of the internal chamberand the pressure of the external chamber are monitored and communicatedto the PLC during the casting process, and wherein the PLC controls thecasting process based on the pressure of the internal chamber and thepressure of the external chamber; wherein the preheating of the crucibleresults in faster heating and subsequent melting of the titanium alloymaterial thereby reducing the time necessary to evacuate the materialfrom the crucible into the mold.
 2. The method according to claim 1wherein the pressurized gas is argon.
 3. The method according to claim 1wherein a frequency generated in the induction coil ranges from 1kilo-Hertz to 50 kilo-Hertz.
 4. The method according to claim 1 whereinan atmospheric pressure of the evacuated internal chamber ranges from3×10⁻² atmosphere to 9.87×10⁻⁷ atmosphere.
 5. The method according toclaim 1 wherein the crucible is a single Yttria-based barium infusedshell layer having a thickness ranging from 0.015 inch to 0.060 inch,and comprised of a binder with a slurry ratio between 1:1.5 and 1:3.5.6. The method according to claim 1 wherein a power level to theinduction coil is more than 70 kiloWatts.
 7. The method according toclaim 1 wherein the titanium alloy ingot is centered within the ceramiccrucible using a centering feature.
 8. The method according to claim 7wherein the centering feature is a plurality of stand-offs in a wall ofthe ceramic crucible.
 9. The method according to claim 1 wherein anatmospheric pressure of the evacuated internal chamber ranges from9.87×10⁻⁷ atmosphere to 9.87×10⁻¹³ atmosphere
 10. A system method forunit cell casting of titanium or titanium-alloys, the system comprising:an external chamber; a ceramic crucible positioned within the externalchamber; an induction centered on the upper third of the titanium alloyingot in the ceramic crucible; an internal chamber positioned within theexternal chamber; and a mold positioned within the internal chamber;wherein the crucible is preheated to a temperature greater than 500° C.;wherein the pressure of the internal chamber and the pressure of theexternal chamber are monitored and communicated to the PLC during thecasting process, and wherein the PLC controls the casting process basedon the pressure of the internal chamber and the pressure of the externalchamber; wherein the external chamber is evacuated to create anevacuated external chamber wherein the ceramic crucible contains atitanium alloy ingot positioned therein; wherein a pressurized gas isinjected into the evacuated external chamber to create a pressurizedexternal chamber; wherein the titanium alloy ingot is melted within theceramic crucible utilizing induction heating generated by the inductioncoil; wherein the crucible is composed of Silica and coated with aYttria based slurry and stucco system; wherein the internal chamber isevacuated to create an evacuated internal chamber; wherein the titaniumalloy material is completely transferred into the mold from the crucibleusing a maximum pressure differential created between the externalchamber and the internal chamber.
 11. A method for unit cell casting oftitanium or titanium-alloys, the method comprising: pre-heating aceramic crucible to a temperature greater than 500° C.; evacuating anexternal chamber to create an evacuated external chamber wherein theceramic crucible contains a titanium alloy ingot is positioned therein;evacuating the internal chamber to create an evacuated internal chamberhaving a pressure no greater than 3×10⁻² atmosphere; melting thetitanium alloy ingot within the ceramic crucible utilizing inductionheating generated by an induction coil wherein a position of theinduction coil begins at a upper third of the titanium alloy ingot andduring the melting of the titanium alloy ingot the position of theinduction coil is lowered relative to the titanium alloy ingot toterminate at a bottom of the titanium alloy ingot; injecting apressurized gas into the evacuated external chamber to create apressurized external chamber with a pressure in excess of 1 atmosphere,wherein the pressure differential is at a maximum; and utilizing a highpressure differential between the external chamber and the internalchamber to flow the completely melted titanium alloy material into themold from the crucible.
 12. The method according to claim 11 wherein thepressurized gas is argon.
 13. The method according to claim 11 wherein afrequency generated in the induction coil ranges from 1 kilo-Hertz to 50kilo-Hertz.
 14. The method according to claim 11 wherein an atmosphericpressure of the evacuated internal chamber ranges from 3×10⁻² atmosphereto 9.87×10⁻⁷ atmosphere.
 15. The method according to claim 11 whereinthe titanium alloy ingot is centered within the ceramic crucible using acentering feature.
 16. The method according to claim 11 wherein theinternal chamber is preheated at a temperature ranging from 1150° C. to1250° C.
 17. The method according to claim 11 wherein a PLC determineswhen to melt the titanium alloy based on the pressures of the internalchamber and the external chamber.
 18. The method according to claim 11wherein the PLC determines when to change the pressure of internalchamber and the external chamber.
 19. The method according to claim 11wherein an atmospheric pressure of the evacuated internal chamber rangesfrom 9.87×10⁻⁷ atmosphere to 9.87×10⁻¹³ atmosphere
 20. The methodaccording to claim 15 wherein the centering feature is a plurality ofstand-offs in a wall of the ceramic crucible.